Carriage drive mechanism

ABSTRACT

A drive mechanism applicable to high-speed printing apparatus for moving a printing carriage along a path in one direction at a specified rate of travel and for returning the carriage in the opposite direction at a substantially higher rate of travel. The mechanism includes a rotating shaft having helical grooves running axially therealong in both directions, one groove being of a certain depth and the other groove being of a lesser depth. A drive pin rides in the deeper groove along the rotating shaft to move the carriage at the specified rate in the printing operation thereof, and the pin rides in the shallow groove to provide a positive return for the carriage at the higher rate in the nonprinting, or return-to-start operation thereof.

limited States Patent [72] Inventors Earl W. McFeaters Kettering; James P. Donohue, l allmrrr, both of 01110 [21] Appl. No. 868,779 [22] Filed Oct. 23, 1969 [45] Patented lllec.21,1971 [73] Assignee The National Cash Register Company Dayton, Ohio [54] CARRIAGE DRIVE MECHANISM 11 Claims, 5 Drawing Figs.

[52] 10.5. C1 197/90, 101/93 C, 74/57 [51] Int. B41j1l9/20 [50] Field of Search 197/82, 84, 84 A, 84 B, 89, 90; 101/93;74/57, 58,59

[56] References Cited UNlTED STATES PATENTS 3,406,625 10/1968 Chamness et a1 101/93 C 2,321,828 6/1943 Lane 74/57 2,441,596 5/1948 Reitter 74/57 2,470,888 5/1949 Degner.. 74/57 2,578,771 12/1951 Zint.... 197/82 2,701,632 2/1955 Zint 197/84 R Primary Examiner-Ernest '1. Wright, Jr. Attorneys-- Louis A. lfiline, Wilbert Hawk, Jr. and George J.

M uclrenthaler AESTEACT: A drive mechanism applicable to high-speed printing apparatus for moving a printing carriage along a path in one direction at a specified rate of travel and for returning the carriage in the opposite direction at a substantially higher rate of travel. The mechanism includes a rotating shaft having helical grooves running axially therealong in both directions, one groove being of a certain depth. and the other groove being of a lesser depth. A drive pin rides in the deeper groove along the rotating shaft to move the carriage at the specified rate in the printing operation thereof, and the pin rides in the shallow groove to provide a positive return for the carriage at the higher rate in the nonprinting, or return-to-start operation thereof.

PATENTEU BECZI ml ENTORS INV EARL W McFEATERS 8| JAMES P DON UE a? M "I! a THElR ATTORNEYS .CAlklhlAGE DRIVE MECHANISM BACKGROUND OF THE INVENTION In high-speed printing machines of the type having laterally moving components, various ways and means have been devised to drive the printing carriage or like mechanism in its travel back and forth across the machine. In the matter of driven devices, a cylindrical cam or grooved shaft, having rightand left-hand grooves, has been used to produce a uniform reciprocating motion, such as the type of structure popular in the level-wind mechanism on fishing reels. Rightand left-hand threaded shafts have also been used in clutchtype control mechanisms to effect engagement and disengagement of a driving shaft and a printing-mechanism driven shaft, or to provide forward and reverse rotation of such a driven shaft. In the case of automatic typing machines, one example provides a threaded rod or shaft which carries a typing head in the form of a wheel having characters thereon located in a helical path, wherein the shaft and the wheel are rotatingly driven and the carriage is moved across the paper as typing progresses, with the carriage being spring returned at the end of the line, all as shown in US. Pat. No. 2,843,243, which issued July l5, I958, on the application of Earl E. Masterson. TI-Ie concept of a grooved cam having shallow and deep grooves and a hydraulically actuated cam follower riding in the grooves for driving a movable member to and fro is found in U.S. Pat. No. 3,080,765, which issued Mar. 12, 1963, on the application of Paul T. Eisele. Another example of a convolutegrooved drive cylinder with spring return is disclosed in U.S. Pat. No. 3,151,547, which issued Oct. 6, I964, on the application of Gunter Wilhelm Robert l-lornauer and Horst Georg Gunter Denzin. Additionally, the prior art shows a printing arrangement for high-speed teleprinters which includes a spindle shaft having two endless superimposed worm gears for printing and for return operations of a carriage, as taught in US. Pat. No. 3,167,166, which issued Jan. 26, 1965, on the application of Werner Schiebeler. And finally, the concept of a rotatable shaft having a helical groove with varying pitch for start, print, and reverse operations of the carriage with spring return thereof is shown in U.S. Pat. No. 3,406,625, which issuedOct. 22, 1968, on the application of Leland D. Chamness and Andre F. Marion. Although these prior art arrangements accomplish the specific results for which they were intended, in that the majority of the drives depend upon a controlled movement in the printing operation, they leave the carriage return in a state of uncontrolled movement by means of the return spring. The to-and-fro movement of the carriage in the prior art is not positive to the extent that the return movement depends upon an uneven force driving the carriage in the nonprinting, or return-to-home operation.

SUMMARY OF THE INVENTION The present invention relates to a carriage drive mechanism and more particularly to a positive drive for moving the printing member in both the printing and nonprinting operations. THe mechanism is especially applicable to high-speed printers capable of laying down a plurality of character imprints per second; for instance, in the range of 30 to 50. It is, of course, realized that at these speeds the transversing movement of the carriage across the machine must be even, positive, and controlled in such a manner as to provide a clear record of the input information.

In the more important aspects of the invention, wherein it is desirable to effect a continuous, or single-cycle operation of a carriage device from a continuously rotating member, the mechanism includes a drive shaft having a multiple-tum cylindrical cam with both a right-hand groove and a left-hand groove, one groove being provided with a greater depth than the other. At one end of the cam is an idling groove joining with a start portion groove, which, in turn, joins with a print portion groove of a constant pitch and which is substantially the length of the cam. At the other end of the cam is a reverse portion groove which joins with a return groove of lesser depth than that of the print groove. The return groove, also substantially the length of the cam, is of increased pitch to propel the carriage at an increased rate of travel back to the idle portion groove. The cam follower is a drive pin supported from the carriage device and having a specially shaped tip for riding in the deeper grooves during printing operation of the carriage device and for crossing over the deeper grooves when riding in the lesser depth grooves during the return trip of the carriage within the cycle.

In view of the above discussion, the principal object of the present invention is to provide a drive mechanism for a printing machine that positively drives the carriage in both the printing and the nonprinting operations.

Another object of the present invention is to provide a cam shaft having deeper grooves, for accepting a drive pin follower in the carriage printing operation, and shallow grooves, for acceptin g the follower in the carriage nonprinting operation.

A further object of the present invention is to, provide a mechanism having cooperating cam and follower means for driving a carriage at a specified rate of travel in one direction and for positively returning the carriage at an increased rate of travel in the reverse direction.

An additional object of the present invention is to provide varying pitch cam means for smooth transition of the carriage during its travel from start to print, from print to reverse, from reverse to return, and from return to start operational positions.

Additional advantages and features of the present invention will become apparent and fully understood from a reading of the following description taken together with the annexed drawing, in which:

FIG. I is a top plan view of part of a printing machine incorporating the present invention;

FIG. 2 is a front elevational view of the structure shown in FIG. 1;

FIG. 3 is a view, in partial section, taken on the line 3-3 of FIG. 2;

FIG. 4 is a fragmentary view of the specially shaped carriage drive pin; and

FIG. 5 is an end view ofthe drive pin of FIG. 4.

Referring to FIGS. I and 2, there is shown part of a printing apparatus which includes a preferred embodiment of the present invention, the apparatus having side frames or plates 10 and 12 spaced from each other to provide support for a platen I4 rotatably carried therebetween, and also to provide support for a drive mechanism, generally designated as I6, extending across the machine and parallel. to the platen I4. The drive mechanism 116 includes a cylindrical shaft 18 suitably journaled by means of bearing hubs 20 and 22 secured to the side plates 10 and 12. The shaft 13 is caused to be rotated by means of a pulley 23 secured to a reduced end portion of the shaft 18, there being a belt 24 around the pulley 23 for driving the shaft, which belt 24 is connected to an electric motor (not shown). A carriage 26 encircles the shaft 18 and is arranged, through use of a guide bushing 27 (FIG. 3), for sliding movement therealong, the carriage 26 including typing or printing mechanism 28, which may take the form of a bar printer arranged for striking against the platen M, as shown, or a type hammer arranged for striking against a typewheel without the need of a platen-again of well-known construction. In the embodiment shown, paper or other record material 30 (FIG. 3) along with carbon paper, if required, runs in a path between the platen M and the printer 28 as the carriage 26 is moved along the shaft 18 during the printing operation.

The shaft llll contains camming grooves for a portion therealong, beginning with an annular groove 35 near the right-hand end thereof (FIG. 2), which groove 35 is termed an idling groove, for receiving one end of a drive pin 36 when the shaft 118 is rotating without the printing operations being performed; that is, the carriage 26 being in a rest position when the drive pin 36 is riding in the groove 35. Connected with the idling groove 35 and with a drive or printing groove 37 is a variable-pitch groove 38 (FIG. 2), in which the drive pin 36 rides at the beginning of printing operations, the groove 38 passing from the idiing groove 35 to a deeper level to connect with the deeper printing groove 37. The printing groove 37 extends a major distance along the shaft 18 in continuous helical fashion, the groove 37 being relatively deep to insure that the end of the pin 36 is sufficiently engaged to ride therein for the purpose of driving the carriage 26 along the platen l4.

Near the left end of the shaft 18 (FIG. 1), the deep printing groove 37 ramps radially' outwardly in a reverse portion groove 41 to connect with a return groove 39, which is not as deep as the printing groove 37 but which has a pitch approximately four times that of the printing groove 37. The reverse portion groove 41 steers the drive pin 36 from the printing groove 37 to the return groove 39 by simultaneous deceleration and ramping from one level to another. Near the righthand end of the shaft 18, the shallow return groove 39 passes through a variable-pitch portion and into the idling groove 35, which, as seen in FIG. 2, is deeper than the return groove 39. It is thus seen that the drive and return grooves actually constitute an endless cam on the shaft 18.

The drive pin 36 is slidably contained within the carriage 26, with the slidable movement being controlled by means of a pivoted hammer 45 actuated by an electromagnet 46, and with a detent ball 47 engaging with one of two annular grooves 48, 49 and properly tensioned therein by a spring 50 and an adjusting screw 51. The carriage 26 is carried along and supported from the shaft 18 and is maintained in alignment and orientation by means of rollers 55 and 56 riding along a support shaft 57 (FIG. 3), the roller 56 being adjustable to maintain proper spacing and evenness of the carriage 26 in relation to the paper 30 and the platen l4.

FIGS. 4 and shown the drive pin 36 having a flattened tip portion 58 terminating in the form of a pointed-end ellipse. This structure readily enables the pin 36 to ride in the endless groove and to cross over the intersecting portions of the deep and shallow grooves 37 39 respectively, in its to-and-fro travel in the carriage printing and nonprinting operations. The round body of the pin 36 enables it to turn within the'carriage 26 as the pin tip portion 58 is guided by the various shaft grooves.

in the operation of the drive mechanism 16 for the carriage 26, it is assumed that the shaft 18 is turning with the drive pin tip portion 58 riding in the idling groove 35, as best seen in FIG. 2, and with the ball 47 in the groove 48, waiting for a signal to commence printing. At the beginning of the printing cycle, the drive pin 36 is actuated to move upwardly into a deeper portion of the idling groove 35 and proceed from the idling groove 35 into the deeper printing groove 37. This movement takes place in the start and accelerate groove portion 38 and occurs within approximately one half-revolution of the shaft 18. Although not shown, a permanent magnet may be fixed to the cam shaft 18, and a stationary reed switch or other sensing device, familiar to those skilled in the art, may be positioned nearby to providean indication of the start position of the shaft 18, so as to properly engage the drive pin 36 therewith upon receipt of the print signal. Since the drive pin 36 is round, it can readily turn to enable the tip portion 58 to follow the path of the grooves 37, 39 in the variable-pitch portions, portions 38 at one end of the shaft between the idle position and the printing position, and portion 41 at the other end of the shaft 18 between the printing position and the return position. During the printing cycle, the carriage 26 is moved along the platen 14 at a constant rate of travel until the drive pin 36 comes to the decelerate and reverse portion groove 41, which also employs the variable pitch in ramping from the drive or printing groove 37 to the return groove 39. Again, a reed switch or like device (not shown) may provide indication to stop the printing cycle in readiness for the reversing operation. The tip portion 58 continues to ride in the reverse groove 41 as it ramps outwardly to the return groove 39, the drive pin 36 being slidably moved downwardly away from the center of the shaft 18 and the hammer 45 being pivoted to the nonprinting position (FIG. 2), which forces the ball 47 to move back to home across the ridge between the grooves 48 and 49 and to reenter the groove 48 under urgence of the spring 50. The reverse and accelerate groove 41 is, of course, likewise of a variable pitch in connecting with the return groove 39 of increased pitch to speedily move the carriage 26 back to the starting position. The return groove 39 drives the carriage 26 in a positive manner and at a constant speed to the decelerate portion of said groove 39, which, again, is of variable pitch and which connects with the idling groove 35. The variable pitch portions of the grooves 37, 39 at each end thereof enable the drive pin 36 to pass from one groove portion to another with minimum jerking and provide smooth travel for the carriagc 26 during the printing cycle and the return cycle of operation thereof.

The instant design of the drive or cam shaft 18 permits positive control of the carriage 26 throughout the following phases of a complete cycle: start and accelerate, print, decelerate and reversal and accelerate, return, decelerate, and idle. At the start and accelerate portion of the cycle, the electromagnetically actuated hammer 45 depresses the drive pin 36 against the bottom of the'idle position groove 35, which movement of the pin 36 into the deeper portion of the groove 39 causes the detent ball 47, under urgence of the spring 50, to engage the pin groove 49 and fix the drive pin 36 at this deeper level and thereby guide the pin 36 into the variable-pitch portion 38 of the deeper groove 39, which causes the printing mechanism 28 carrying carriage 26 to be accelerated up to printing speed. This start and accelerate portion of the cycle occurs in less than one revolution of the drive shaft 18.

The printing phase of the cycle occurs as soon as the constant pitch portion of the groove 37 has been reached by the drive pin 36. The carriage speed during the printing operation depends upon the rotational speed of the shaft 18 and the pitch of the groove 37, which are set at predetermined values, and this speed is maintained for substantially the length of the grooved portion of the drive shaft 18.

When the reversal portion 41 of the groove 37 os reached, the drive pin 36 follows the variable pitch of the groove to decelerate the carriage 26 to zero lateral movement and then passes into the oppositely turned groove 39 with the variable pitch to accelerate the carriage 26 to the higher return speed. Simultaneously, the depth of the groove 41 decreases at a given rate to automatically guide the drive pin 36 into the shallower groove 39 on the drive shaft 18 while maintaining a positive control for reversal of the carriage 26. Also, during this time, the drive pin 36 is slidably moved within the carriage 26 where the detent ball 47 seats in the groove 48 for the return trip.

Return of the carriage 26 can be set at the same rate as the printing portion of the cycle, whereby the printing and return grooves 37 39 would have the same pitch, thus simplifying the design of the drive shaft 18 in the use of identical rightand left-hand grooves. However, since time is so important in highspeed printing apparatus, it is desirable to return the carriage 26 at a much faster rate by increasing the pitch of the return groove 39. In this respect, and as mentioned above, the return pitch is approximately four times that of the printing pitch.

Near the end of the return phase, the drive pin 36 again follows the variable pitch of the groove 39 to decelerate the carriage 26 smoothly to rest at the idle position, wherein the pin 36 enters the continuous annular groove 35, to run in a path perpendicular to the drive shaft axis, and wherein both the right-hand and the left-hand grooves 37, 39 pass and change in depth. As the drive pin 36 is guided into this annular portion of the groove 35 at the idle position of the mechanism 16, the carriage 26 remains idle in this position while the shaft 18 continues to rotate until such time as the drive pin 36 is moved to the deep portion of the groove 37 for another printing cycle.

It is thus seen that herein shown and described is a drive mechanism which provides positive control for a printing carriage throughout the cycle of printing and nonprinting, and which mechanism accomplishes all the features and advantages as mentioned above. While only one embodiment has been disclosed, certain variations on the above may occur to those skilled in the art, so it is contemplated that all such variations having these features are within the scope of the invention.

What is claimed is:

i. A drive mechanism comprising a frame, a rotating cam means carried by theframe, a carriage movable along the cam means in a cycle of operation, said cam means having an annular groove at one end thereof for idle operation of the carriage, a first helical groove connected with the annular groove and running along the'cam means for advancing the carriage in one direction, and a second helical groove of lesser depth connected with the first helical groove and running along the cam means for returning the carriage in the opposite direction, follower means engageable with the cam means for positive driving of the carriage from an idle position through an advance and return cycle of operation, means for moving the follower means from an idle position in the annular groove into the first helical groove for driving the carriage in the advance portion of the cycle, and means for reversing the direction of drive of the carriage whereby the follower means is moved from the first helical groove to the second helical groove to be guided at the lesser depth for driving the carriage in the return portion of the cycle back to the idle position.

2. The drive mechanism of claim 1 wherein said cam means includes a start portion groove connecting the annular groove with the first helical groove, and said moving means effects transfer of the follower means from said annular groove to said start portion groove.

3. The drive mechanism of claim 1 wherein said reversing means is a reverse portion groove for camming the follower means from the first helical groove to the second helical groove.

l. The drive mechanism of claim ll wherein the second helical groove is of greater pitch than the first helical groove.

5. The drive mechanism of claim ll wherein said first helical groove is of a depth greater than that of said annular groove, said moving means effects transfer of the follower means from said annular groove to said first helical groove, said second helical groove is connected with said annular groove, and said second helical groove is of a depth approximately that of said annular groove.

6, in printing apparatus, the combination of a platen, a printer carriage movable along the platen, and means for driving the carriage to and fro in an advance and return cycle of operation, said driving means comprising a rotating cam member supported from the apparatus, a drive pin carried by the carriage and engageable with the cam member throughout the cycle of operation, said cam member having an annular groove at one end thereof and an endless helical groove of a predetermined depth runningalong the cam member in one direction from said annular groove and of lesser depth running along the cam member in the other direction to said annular groove, means for moving the drive pin at the start of a cycle of operation from the annular groove into the endless groove of predetermined depth for advancing the carriage in said one direction, and means for moving the drive pin from the groove of predetermined depth into the groove of lesser depth for returning the carriage in said other direction and positioning the drive pin for return to the annular groove at the end of the cycle of operation.

'7. The combination of claim 6 wherein the cam member includes a variable pitch groove connecting the annular groove with the groove of a predetermined depth.

d. The combination of claim t3 wherein the cam member includes a variable-pitch reverse groove for camming the drive pin from the predetermined depth groove into the groove of lesser depth.

9. A drive mechanism for a high-speed .printer having a frame, a platen rotatably supported from the frame, a carriage movable along the platen in a cycle consisting of printing and return portions of operation, and printing mechanism carried by the carriage and capable of imprinting on the platen during at least the printing portion of the cycle, said drive mechanism comprising a continuously rotating cam member supported from the frame and having a deep helical groove extending along the cam member in one direction and a shallow helical groove extending in the opposite direction, an annular groove at one end of the cam member for idle operation of the carriage and a variable-pitch groove connecting the annular groove with the deep helical groove, a drive element guidable in the annular groove during idle operation of the carriage and engageable with the helical grooves throughout the cycle of operation, means for moving the drive element from the annular groove along the variable-pitch groove and into the deep helical groove for driving the carriage in advancing manner during the printing portion of the cycle, and means for moving the drive element from the deep helical groove into the shallow helical groove for driving the carriage in reverse manner during the return portion of the cycle, the drive element being positioned upon return of the carriage at a groove depth compatible with that of the annular groove.

iltll. Tl-ie drive mechanism of claim it wherein the means for moving the drive element from the deep helical groove into the shallow helical groove includes a variable-pitch reverse groove for automatic transferring of the drive pin from one to the other groove.

M. The drive mechanism of claim 9 wherein the shallow helical groove is of greater pitch than the deep helical groove for fast return of the carriage. 

1. A drive mechanism comprising a frame, a rotating cam means carried by the frame, a carriage movable along the cam means in a cycle of operation, said cam means having an annular groove at one end thereof for idle operation of the carriage, a first helical groove connected with the annular groove and running along the cam means for advancing the carriage in one direction, and a second helical groove of lesser depth connected with the first helical groove and running along the cam means for returning the carriage in the opposite direction, follower means engageable with the cam means for positive driving of the carriage from an idle position through an advance and return cycle of operation, means for moving the follower means from an idle position in the annular groove into the first helical groove for driving the carriage in the advance portion of the cycle, and means for reversing the dirEction of drive of the carriage whereby the follower means is moved from the first helical groove to the second helical groove to be guided at the lesser depth for driving the carriage in the return portion of the cycle back to the idle position.
 2. The drive mechanism of claim 1 wherein said cam means includes a start portion groove connecting the annular groove with the first helical groove, and said moving means effects transfer of the follower means from said annular groove to said start portion groove.
 3. The drive mechanism of claim 1 wherein said reversing means is a reverse portion groove for camming the follower means from the first helical groove to the second helical groove.
 4. The drive mechanism of claim 1 wherein the second helical groove is of greater pitch than the first helical groove.
 5. The drive mechanism of claim 1 wherein said first helical groove is of a depth greater than that of said annular groove, said moving means effects transfer of the follower means from said annular groove to said first helical groove, said second helical groove is connected with said annular groove, and said second helical groove is of a depth approximately that of said annular groove.
 6. In printing apparatus, the combination of a platen, a printer carriage movable along the platen, and means for driving the carriage to and fro in an advance and return cycle of operation, said driving means comprising a rotating cam member supported from the apparatus, a drive pin carried by the carriage and engageable with the cam member throughout the cycle of operation, said cam member having an annular groove at one end thereof and an endless helical groove of a predetermined depth running along the cam member in one direction from said annular groove and of lesser depth running along the cam member in the other direction to said annular groove, means for moving the drive pin at the start of a cycle of operation from the annular groove into the endless groove of predetermined depth for advancing the carriage in said one direction, and means for moving the drive pin from the groove of predetermined depth into the groove of lesser depth for returning the carriage in said other direction and positioning the drive pin for return to the annular groove at the end of the cycle of operation.
 7. The combination of claim 6 wherein the cam member includes a variable pitch groove connecting the annular groove with the groove of a predetermined depth.
 8. The combination of claim 6 wherein the cam member includes a variable-pitch reverse groove for camming the drive pin from the predetermined depth groove into the groove of lesser depth.
 9. A drive mechanism for a high-speed printer having a frame, a platen rotatably supported from the frame, a carriage movable along the platen in a cycle consisting of printing and return portions of operation, and printing mechanism carried by the carriage and capable of imprinting on the platen during at least the printing portion of the cycle, said drive mechanism comprising a continuously rotating cam member supported from the frame and having a deep helical groove extending along the cam member in one direction and a shallow helical groove extending in the opposite direction, an annular groove at one end of the cam member for idle operation of the carriage and a variable-pitch groove connecting the annular groove with the deep helical groove, a drive element guidable in the annular groove during idle operation of the carriage and engageable with the helical grooves throughout the cycle of operation, means for moving the drive element from the annular groove along the variable-pitch groove and into the deep helical groove for driving the carriage in advancing manner during the printing portion of the cycle, and means for moving the drive element from the deep helical groove into the shallow helical groove for driving the carriage in reverse manner during the return portion of the cycle, the drive element being positioned upon return of the Carriage at a groove depth compatible with that of the annular groove.
 10. THe drive mechanism of claim 9 wherein the means for moving the drive element from the deep helical groove into the shallow helical groove includes a variable-pitch reverse groove for automatic transferring of the drive pin from one to the other groove.
 11. The drive mechanism of claim 9 wherein the shallow helical groove is of greater pitch than the deep helical groove for fast return of the carriage. 